The present invention relates generally to an end of product life indicator or a time duration indicator for products that include a volatile component. More specifically, the present invention relates to the use of a volatile dye as an end of product life indicator or a time duration indicator.
Substrates have been commonly used as carriers for air-treating compounds, such as insecticides, insect repellents, fragrances and deodorizing compounds. Insect repellent impregnated substrates and insecticide-impregnated substrates are useful in both residential and commercial settings to reduce or eliminate pests. Substrates impregnated with fragrances and deodorizing compounds are also useful in both residential and commercial settings to reduce or eliminate offensive odors and to provide a long-lasting pleasant odor. Volatile products may also be combined and impregnated into a substrate for combined purposes such as insect control and deodorization. A variety of different substrates are available and are known to those skilled in the art.
One disadvantage associated with the use of volatile components impregnated into a substrate is that the consumer is often unaware as to when the volatile component is depleted or exhausted. As a result, the consumer is unable to determine when to replace the product. The problem is compounded when the volatile product is a low odor or odor free insecticide. However, even when the volatile product is a fragrance or a deodorizing composition, consumers are often unable to determine when the product should be replaced for optimum product performance. Specifically, when relying upon the sense of smell, it is difficult to determine when a fragrance or a deodorizing component has been substantially depleted to a point where the product is no longer effective.
U.S. Pat. No. 4,921,636 teaches a visual indicator whereby the carrier or substrate is transparent or translucent when impregnated with a volatile product containing a solvent. As the solvent evaporates, the substrate or carrier becomes more opaque thereby providing a visual end of product life indicator for the consumer. However, this visual end of product life indicator is problematic because of the insufficient contrast between a light or white carrier and a partially transparent translucent carrier. A preferable indicator would include a sharp color change.
A color change indicator is disclosed in U.S. Pat. No. 4,824,827, assigned to the assignee of the present application. The color change taught in the ""827 patent depends upon a pH change. The dye utilized is substantially non-volatile.
According to one aspect of the present invention, a time duration indicating system for a product that includes a volatile component comprises a substrate and a volatile dye. The substrate is coated with the volatile dye thereby coloring the substrate. As the volatile dye evaporates over time, the substrate changes color.
According to a further aspect of the present invention, a method for indicating an end of life for a product that includes a substrate impregnated with a volatile component comprises the step of coating a substrate with a volatile dye thereby coloring the substrate. As the volatile dye volatilizes over time, a color change of the substrate results.
According to yet another aspect of the present invention, an insecticide product with an end of life color change indicator includes a substrate and a volatile insecticide coated onto the substrate. The volatile insecticide is selected from the group consisting of transfluthrin, vapothrin, permethrin, prallethrin, tefluthrin and esbiothrin and guaiazulene is coated onto the substrate.
Other aspects and advantages of the present invention will become apparent upon consideration of the following detailed description.